Advances in the general area of sewage treatment has resulted in the realization that, under properly controlled conditions, animal wastes and the like may be broken down into components that can be used as fertilizer or may be disposed of without creating either a health hazard or a pollution problem. Bacterial breakdown of sewage waste material is essentially performed by one of two basic processes; namely, aerobic and anaerobic. The latter process does not require oxygen and is therefore the prevailing process by which bacterial breakdown occurs where any substantial accumulation of waste is present, such as in manure lagoons (used by farmers to a limited extent), septic tanks, hog houses and the like. While manure or animal waste will eventually break down and be oxidized, the anaerobic process is accompanied by the production of noxious gases and has other disadvantages as well.
The aerobic process is performed by oxygen requiring aerobic material and has numerous advantages over the anaerobic process. For example, chemical breakdown is achieved by aerobic bacteria without the generation of objectionable odors. Moreover, the process does not attract flies or other vermin and the fertilizer value in the processed liquid is also retained. However, aerobic bacteria needs a constant supply of oxygen on which to thrive and, therefore, such aerobic systems require continuous replenishment of dissolved oxygen consumed by the aerobes in the waste material. Additionally, agitation is necessary to prohibit waste particles from settling out and resisting bacterial decomposition.
These requirements of aerobic systems have given rise to numerous mechanical aerators and agitators, including designs similar to those used in commercial sewage treatment plants. For example, devices have been created to aerate the material by rotating paddle wheels or the like which operate to either beat air into the material while moving it in the reservoir or to at least partially throw the material into the air. Other designs have incorporated separate means for moving the material in the reservoir and have introduced air by pumping compressed air through permeable "air stones" positioned at the bottom of the reservoir. The air stones are adapted to break the air into bubbles which enter the waste material. Bubbles are prepared over a stream of air passing through the material because the ratio of surface area to volume is greater and enables the oxygen to be more easily dissolved in the material. The proper function of an aerobic system is, of course, dependent upon the quantity of dissolved oxygen that is present within the waste material. It is seen that more power should be consumed by injecting larger than necessary quantities of oxygen into the material and, therefore, economic considerations are important in the manner in which oxygen is introduced. Another important economic consideration involves the manner in which the material is moved around or circulated within the reservoir.
In the past, certain U.S. patents have described various systems for the aeration of such septic tanks. For example, U.S. Pat. No. 3,778,233, issued on Dec. 11, 1973, to Blough et al., describes a device for aeration used primarily in confinement livestock operations to aerate sludge pits used in conjunction with the same. This apparatus included an elongated hollow shaft having a propeller secured to its lower end and driven at its upper end by a motor mounted on a swingable frame. Air enters the upper end of the shaft and exits adjacent the propeller. Rotation of the shaft and propeller induces air into the material. The shaft is immersed in the material at an angle to break the air into a multitude of fine bubbles while simultaneously moving the material around the reservoir. Since this device was designed under the circumstances of confinement feeding operations for livestock, such as hogs, there were limitations with the use of such device in conjunction with septic tanks that are used for storing human wastes.
One of the problems with sewage disposal plants, and septic tank plants, are that often the disposal system finds itself "contaminated" with non-organic non-biodegradable waste materials such as bandages, sanitary napkins, disposable diapers, condoms, and other material that people often discard into the lines of a sewage system. These adulterating materials could be drawn into the propeller of the aeration device described in U.S. Pat. No. 3,778,233. As a result, the propeller would become entangled in those materials and would plug the air tube lines. As a result, aeration would not be successfully achieved and, at best, the sludge material is simply stirred or agitated by the propeller with little effect on biodegradation.
In an effort to solve this problem, the inventor of U.S. Pat. No. 3,778,233 devised another apparatus for the aeration of septic tanks. This apparatus was described in U.S. Pat. No. 5,194,144, issued on Mar. 16, 1993. This patent describes an aeration device for septic tanks which includes an elongated shaft with a motor associated with the upper end of the shaft for rotating the shaft. An axial thrust propeller is rigidly attached to the shaft for rotation therewith. An air tube surrounds the shaft for drawing ambient air from the upper end of the shaft downwardly around the propeller when the propeller rotated in the septic tank waste so as to provide fine air bubbles. A guard bushing is concentrically positioned in the air tube to allow free escape of air bubbles into the agitated septic waste material to aerate such materials. The guard bushing was designed so as to prevent non-organic waste adulterants, such as non-biodegradable plastic and rubber materials, from being drawn into the propeller.
Unfortunately, this system can result in certain long-term problems associated with the treatment of such waste. The actual use of the guard bushing around the shaft will, over time, eventually become plugged with the waste materials. When the bushing becomes sufficiently plugged, it will eventually burn out the motor by the resistance to the rotation of the shaft of the motor. Additionally, this particular technique of introducing air does not allow for an easy control of the air flowing to the propeller. Furthermore, installation of such a device is quite complex. First, the concrete walls of the septic tank must be penetrated so as to create an opening for the apparatus. Once a hole is formed in the concrete, the device must be properly sealed to the walls of the treatment tank. If any flooding would occur within the wastewater treatment tank, such water could enter the interior of the chamber in which the motor is mounted so as to burn out the motor. Finally, complicated procedures would be required for maintenance and repair if the air tube should become plugged or the device would otherwise require replacement or repair.
It is an object of the present invention to provide an aeration device which can be easily mounted in association with existing septic tanks and wastewater treatment tanks.
It is another object of the present invention to provide an aeration device which will be water proof in the event of flooding.
It is a further object of the present invention to provide an aeration device which does not require the formation of an extra entrance hole on the wastewater treatment tank.
It is a further object of the present invention to provide an aeration system which uses existing riser openings associated with the wastewater treatment tank.
It is a further object of the present invention to provide an aeration device which avoids the use of any bushing materials which can be subject to plugging or failure.
It is still another object of the present invention to provide an aeration device for a wastewater treatment tank which allows for a simple control of air flow to the wastewater.
It is still another object of the present invention to provide an aeration device which can be easily accessed, simpler to use, easier to mount, simple to manufacture, and relatively inexpensive.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.